1. Field of the Invention
The present invention relates to an articulating marsh buggy in the form of an amphibious vehicle incorporating forward and rear drive units which are pivotally connected for relative angular movement about a vertical axis and oscillatable about a longitudinal axis. Each of the drive units includes a pair of pivotal, floatable pontoons with each pontoon including a drive chain on which cleats are mounted. The drive chains are driven by independent motors to enable the vehicle to move over various ground terrains and be propelled in marshy areas, bayous or water bodies by cleats on the driven chains on the pontoons.
2. Description of the Prior Art
Amphibious marsh buggies or vehicles were first developed about 50 years ago. One use of these vehicles was to support oil and gas exploration. The vehicles originally developed for this task were equipped with four large wheels and two engines. These wheels were designed with deep lugged cleats for traction and built of light weight steel for durability and buoyancy. The drive engines were installed on the right and left sides of the vehicles' main frame. Each engine powered the two wheels on their respective sides. Steering or turning was achieved by increasing and/or decreasing engine speeds which in turn controlled wheel revolutions and made turning possible. For example, if the driver was required to turn the vehicle to the right, this was accomplished by increasing engine and wheel RPMs on the left side and vice versa to turn left.
A short time after these vehicles were put into service it was determined that their environmental impact was so destructive that they were banned. This led to the development of a second generation vehicle which incorporated the use of pontoons and a track drive system. Each unit was configured with two longitudinal side pontoons which provided the required buoyancy and a continuous drive track around each pontoon provided drive power. Channel type cleats were provided on the drive tracks for traction, with both tracks being driven by a single engine. This track drive system also incorporated a unique braking system to control steering. This type of steering system requires the driver to lock or stop the track movement on one side while allowing the other side to continue pulling. This concept is similar to the steering system used on bulldozers and cranes.
As with all vehicles equipped with this type steering system, when turning right for instance, it is necessary to lock or stop track movement on the right side while pulling with the left side. Therefore, in order to turn it is necessary to develop sufficient pulling force and traction on one side to overcome not only the weight of the unit, but also the drag resistance of the locked tracks on the opposite side. When this turning or "skidding" method is used in ecologically sensitive areas, where tender vegetation and loose root structure exist, the results are disastrous. These units, designed and built in the 1960's, have undergone little improvement to date and are still the primary means of support utilized by the oil and gas industry.
The following U.S. patents may be pertinent to the vehicle of the present invention:
______________________________________ 3,435,908 3,789,942 4,174,757 3,443,654 3,937,289 4,645,023 3,451,494 4,072,203 4,966,242 ______________________________________
However, the above patents do not disclose the structural arrangement and operational characteristics of the present invention.